Testing Early '80s Malaysian and Japanese TI RC4558P Opamps With a Modded Tube Screamer

One sort of thing we have here at the Alley Gadget Shop is gadgets. Lots of them. Everything from a small, beautifully hand forged cable pulley made for an ancient French bicycle, to odd assorted guitar parts, obsolete Macintosh computers, and old tube amps and other vintage audio gear from the last century. Some work, most need repair, and a few are unfixable; and whatever is really dead often gets repurposed or dismantled for usable parts rather than just getting tossed.

Case in point was an interesting (and ugly) looking but totally defunct audio unit from the 1980s. Didn't work, no way it was ever going to be fixed, so we poked around for salvageable stuff. Besides a power cable, fuse holder, knobs and some assorted oddments, there were a few various integrated circuit chips, all in sockets. Most were 4558 type dual operational amplifier (opamp) ICs.

Texas Instruments RC4558P, made in Malaysia, 49th week of 1982:

Texas Instruments RC4558P, contract manufactured for TI by Japan Radio Corporation, 31st week of 1982:

Texas Instruments RC4558P, made in Malaysia, 1st week of 1983:

Other component manufacture date codes in this circuit, all from mid '82 to early '83, and a QC sticker on the chassis dated April 1983, correlates with the IC codes.

It might be a good idea to test those ICs, and see what shape they're in. But how?

Making a Temporary Test Rig

Hanging around the audio and art production space at the ol' Gadget Shop, is a mid-'90s Ibanez TS5 Soundtank series Tube Screamer, with TS808 circuit mods expertly done by David in Massachusetts. It's as good as any Screamer I've ever plugged into, tonally indistinguishable from the really great sounding 808 T.S. section in a stock early '80s Ibanez UE 300 multi-effector I happen to own and use.

When he did the mods, David installed a socket for the 4558 IC, and popped in a newer production TI RC4558P:

This makes it easy try out different ICs, and we took advantage of the socket to perform real time audio functionality testing on the three different sub-types of the Texas Instruments RC4558P that were salvaged.

To make a handy temporary test rig, the bottom plate and the control knobs were removed from the modded TS5 Tube Screamer, and the component board dropped smoothly away from the pedal body, allowing easy access to the IC socket:

An AC adapter was plugged in, the Screamer's output hooked up to an amp, and one by one we tested 24 RC4558P opamp ICs, including the one already in the TS5, while playing a variety of diverse sounding guitars:

We didn't bother reassembling the TS5 between each RC4558P test - just turned the amp volume down, shut off the AC strip the pedal power supply was plugged into, swapped the chip, and powered it all back on again. This way, testing impressions stayed fresh from chip to chip - it took longer to switch guitars than it did ICs.

Test Results, and a Cold Marguerita

Obviously, doing real time in-circuit testing of dual opamps, using an improvised and fairly inexpensive test rig, is by its nature non-scientific - we're not going to get any key parameter measurements like Vos, CMRR, Iq, etc. Our main goal was operational functionality testing - does a particular IC actually work, without any issues, in a typical example of a well known overdrive pedal circuit?

Main takeaways from today's testing:

1) With only one failure, all of the opamp ICs evaluated checked out okay, with the TS5's overdrive effect behaving itself in a predictable manner throughout the range of each of the three control pots.
2) All four TI RC4558P variants sounded fine in-circuit, with no fatal audio flaws: tonal and/or level degradation, glitches, or weird sonic artifacts.
3) There appeared to be very subtle audio differences between the four sub types of TI RC4558P we had, mainly in the overall amplification levels and possibly slightly differing low-end coloration. A couple times we went back and did multiple A/B comparisons between two particular ICs, just to make sure we weren't imagining those slight variations.

It might have been nice to have other brands, sub types and eras of 4558 chips, in order to compare them with the 1980s Texas Instruments ICs on hand. Possibly 4558s from other makers might have differing audio characteristics, and that's an idea for further testing in the future. But heck, forget about all that. It's late afternoon on a gorgeous and hot summer day - doesn't a nice cold marguerita sound like just the thing right now?

Yum, looks good...

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If you're at all interested in obtaining one or more of the vintage 1980s Texas Instruments RC4558P tested in the above article, please consider going over to the right hand sidebar of this blog, find the orange rectangle, and click through to the Alley Gadget Shop's internet store at Reverb.

Note: as of July 2021, all of the vintage TI RC4558P ICs for sale had been sold. I hope everyone who acquired one is having fun with pedal projects!

The Hissing Of Summer Sprinklers

In an earlier post about fitting a pickguard and control plate to a reclaimed knotty pine guitar body, I wrote about how hard it was getting any work done on a beautiful and warm late summer day. All I really wanted to do was "move the yard sprinkler and sit with iced tea and watch the day-dreamscape of fantastically shaped huge white cumulus clouds slowly drift across a deep and clear blue Oregon sky". In fact, just seeing droplets of water jet up from the sprinkler, pause momentarily at the tops of their arcs, and plop back down exploding onto the grass, was mesmerizing in itself.

I forced myself awake long enough to go inside, grab a well used Lumix ZS25 pocket travel zoom camera, and take a few pictures of sprinkler drops in mid air.

While a human eye and brain sees each droplet as what it is - an almost round traveling ball of water - the combined photo taking speed of the camera's shutter, flash, and ISO setting turns most of the drops into longish glass eel or transparent snake like shapes. Reflections from the strobe flash on each of the individual water drops also create an illusion of glittering eyes on thousands of translucent flying creatures. Reviewing these pictures in the viewfinder, along with the sound of the sprinklers, made me think of of Joni Mitchell's song (and album title) The Hissing Of Summer Lawns.

In the next photo are time-stretched tubular water droplets, some going up and some traveling down, a few at the very top of their arc, globular and momentarily suspended, and, toward the bottom of the frame, two drops going in opposite directions and colliding head on:

Meanwhile, in another part of the yard, a jar of raspberry and peach sun tea was brewing:

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No doubt, clearer and higher definition photos could have been taken with our much newer Olympus Micro 4/3 camera, but the old Lumix has seen so much action in its relatively long and useful life, that a bit of water splashed on it was no big deal. One of the very best compact cameras ever made, the vast majority of the photos featured in the Origami Night Lamp blog have been taken with the Panasonic Lumix ZS25.

Click or tap on any photo above for larger, higher def images.

Knotty Pine Offset Barncaster Project, Part 3: Pickups and Controls

If you've read the other posts about putting this Offset Barncaster project guitar together (Part 1, and Part 2), you'll notice I assemble at a glacial pace. But the truth is even worse: it was mid November of last year when I saw the NoMoonLaser knotty pine body for sale, fell in love, and impulse bought it with no definite plans for turning it into a playable guitar. Since then, it's sat around like a beautiful old Greek statue with missing body parts, looking at me accusingly and wishing it at least had a neck, while I paid more attention to other projects. But now, it's almost done.

This week the pickups and controls got wired up. Being a hold-over from the dawn of the electric guitar age, a stock Telecaster control plate circuit is very basic, and that's a good thing since there isn't a lot of room within that narrow control rout. Sure, it's possible to put in a 4 or 5-way switch and trick wiring for phase, series and other mods, or making a late 1940s original Broadcaster type wire-up; but this time it'll just be the standard (and simple) 3-way Tele circuit from the mid-50s on:

That big old Sprague "Black Beauty" capacitor is a real tone monster, with a distinct quasi-"wah" sweep. I considered flipping the plate around so the tone control would be more readily accessible for doing that chicken pickin' tone knob roll thing, and I still may. To make that possible in the future, all wires from the pickups were left unclipped.

Besides the tone cap, the rest of the parts are a pair of CTS 250K-A potentiometers, and a Fender brand 3-way switch, which might be made by Oak Grigsby - its design is certainly 1/1 with an Oak switch. On the top of the plate are a pair of weighty high knurl nickel plated brass Gotoh dome knobs, and a Fender "barrel" style switch knob / tip.

An ingenious modern design innovation is the ElectroSocket output jack holder; this one is from Allparts. After soldering up the two output wires, one nut and a washer were put on the threaded barrel of the jack:

Then the jack holder / socket was spun onto the jack and snugly hand tightened prior to attaching it within the body's output jack hole:

The nut + washer stack below the body of the socket/jack holder resulted in lowering the barrel of the jack down almost flush with the bottom of the ElectroSocket's cup. This way, when a cable plug is placed into the cup, the plug tip naturally and effortlessly slides into the jack with a minimum of hunting around. Yep, just stick that tip near the socket, and it slips right in, ready to rock and roll all night long, baby:

After checking the pickups, switch and volume pot with a meter, the next step was setting the distance between the pickups and the strings (pickup height). For a quick initial setup, I prefer using a variation of the European method for setting Stratocaster pickup heights; fretted at the 21st fret, pole piece to bottom of string measurements of each pickup are: bridge p.u. = high E 2mm and low E 3mm, middle p.u. = high E 3mm and low E 4mm, and neck p.u. = high E 4mm and low E 5mm.

Useful with other pickups than just Strats, these are good starting points, with final adjustments made while playing and listening ("by ear"), but often it's okay right off the bat.

The above method assumes the use of vintage style pickup sets - with all pickups identical spec, as they used to be before dedicated position specific pickups with differing output strengths, pole piece magnetic orientations, and coil wire winding directions came along. Unlike Strats, Telecasters almost always had dissimilar pickups, so we would set them up by ear, except for the very first measurement, which was to use a nickle (US 5 cent piece) as a gauge between the high E string and its bridge polepiece. And a new Tom Jefferson nickle is very close to 2mm in thickness:

In the case of the pair of Telecaster pickups used for this guitar, they're well matched: the Fender Vintage '62 bridge pickup metered out at 6.19K, and a Fender Tex Mex neck pickup at 6.11K, and both have the same coil winding direction and pole piece orientation.

High E, bridge pickup, 2mm:

Note the rust on that "new" string; a couple years ago I bought a few sets from a seller on the humid Gulf Coast - a bad purchase. Anyway, now I have various odd and yucky strings for use during set ups. When we're all done, a new non-rusted set of GHS Gilmour 10-48 will be installed on this guitar.

Low E, bridge pickup, 3mm:

Check out the ultra cool white cotton string wrapped and wax dipped coil.

High E, neck pickup, 4mm:

The neck pickup's low E was set to 5mm below the bottom of the string. Note in the above picture the substitute for a finger pressing on the string behind the last fret - a small canvas bean bag filled with tiny steel pellets. An all purpose floppy weight, I've also used it as a stable place to put a compact camera, atop an uneven or sloping surface.

Nest step will be a tonal test at speed, followed by new strings and any needed action and intonation adjustments. After that, we can finally remove the protective plastic film on the pickguard.

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You might be curious about the amplifier in the photo at the top of this post. On loan from my friend David in Massachusetts, it's his own creation, a model that Leo should have made, but didn't. A mid-'60s Fender Bassman head chassis in a custom made 2 x 10 combo cab from JD Newell, it has 50 watts of real, all tube power into a pair of very efficient Eminence Ragin' Cajun 10".

Style wise, David's Bassman combo is also unique, with a variant dark wheat grill cloth, combined with burgundy tolex - a color palette which predates Fender's own burgundy covered models by some years. The ultra rare Maroon Wheat grill material, rescued from a 1955 Baldwin organ, has maroon tinted threads running through the wheat weave, giving a very sculptured, three dimensional effect when seen up close.

Under the hood, an almost completely rebuilt circuit, using many new and old stock parts, stays close to the original AA164 schematic, with the exception of minor yet critical voicing and noise floor lowering mods. The resultant compact (22" x 22") powerhouse is soulful and alive with touch sensitive dynamics, and is incredibly toneful at any position of the volume control on either of the separately voiced input channels, from barely cracked open all the way up to insanely loud, tight and girthy rock tones at 7 or 8 on the dial. All in all, this re-imagined Bassman is a great combination of power, tone, portability, and vintage mojo style.

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All pictures taken with a Lumix ZS25 pocket travel zoom camera. Click or tap on any photo above to access larger, higher def images.

 

Here's a link to the final post in this series, Part 4.

Knotty Pine Offset Barncaster Project, Part 2: Incomplete Parts-O-Caster

In Part 1 of the Knotty Pine Offset Barncaster Project, a 1991 Fender MIM Stratocaster neck was experimentally attached to a cool looking pine Telemaster / Jazzcaster / Offset Telecaster body from NoMoonLaser, along with enough other parts to make a playable prototype, and the results were very good indeed. Enough to go ahead and jump into an "Irrevocable Act", something not easily undone - locating and drilling all the pickguard and control plate mounting screw holes.

I'm kind of really particular about having the various components line up on a Telecaster type guitar, both measurement wise and visually. Do the sides of the bridge plate and neck pocket, and the extended virtual lines extrapolated from the edges of the mounted neck, all fall as nearly equally as possible to the center-line of the body? Will the cutout on the pickguard be close to square with the bridge plate? Is the control plate as parallel as possible to the right hand side of the bridge? And is the neck pickup centered well between both E strings?

One reason for building up with higher quality non-boutique parts, such as Fender, Allparts, Gotoh, and others in that class, is because they almost always just fit, period. In the case of this project, the unknown quantity is the NoMoonLaser body. The main reason I bought it was the fun factor - it looks fantastic, and it was already rustic finished in a nice transparent lacquer. Unlike higher cost bodies from Tone Bomb and Warmoth, NoMoonLaser bodies are hand made, not cut on laser guided CNC milling machines (hence the name?), so the measurements can sometimes be very slightly "off", but nothing that can't be compensated for. It's almost like working with a body that you might have made yourself - not absolutely perfect, yet very well crafted and usable, and it gives you a chance to use those brain cells, and think.

In the end, the only fudging needed was minor: a small bit of sanding on one side of the neck pocket, redrilling the tops of the string though body holes (on the 1st, 2nd, 5th and 6th string holes) to compensate for the difference between 2 1/16" (import spec) and 2 1/8" (vintage spec) string spread dimensions, and widening the control cavity about 1/32" so the control plate sits well with the pickguard.

I also had to trim a small amount from the edge of the Warmoth pickguard's upper "horn" where it meets the neck and neck pocket. That's all, only about 30 minutes work, not counting moving the yard sprinkler and sitting with iced tea and watching the day-dreamscape of fantastically shaped huge white cumulus clouds slowly drift across a deep and clear blue Oregon sky.

It was a beautiful summer day, not too hot, with a light breeze; I set up a couple funky sawhorses out on the back deck and put some well used planks across them, and put an old "camping" towel, folded once, over the planks to make a comfy padded work station. After a few minutes of measuring and thinking, then some sanding, trimming, and re-measuring, it was time to grab the trusty Snappy brand self centering 5/64" drill bit - perfect for quick, accurate, and fear free drilling of pilot holes in the body for components with counter sunk mounting holes, such as Tele bridge plate, pickguard, and control plate.

After drilling those holes with the Snappy, twisting the new mounting screws in was a breeze - slowly and by hand. * Tip: Using a real screwdriver, not an electric tool, helps to ensure keeping those screws as vertical as possible. If you use a powered drill or driver when running screws into soft wood, like old pine, it's way too easy to get them in crooked, or stripping the wood and enlarging the pilot hole. Also, when the screw is down flush with the counter-sink in the 'guard or plate, you're done - don't over-tighten, especially in soft wood.

Welp, today's work fun turned out really well. Now, there's only a few quick things left to do before we're finished with this knotty pine offset Barncaster project: wire up the switch and pots on the control plate and run a wire to the output jack, put on a new set of strings, and do the final adjustments on the string action and neck relief, pickup height, and intonation. After that, plug in and play.

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Click or tap on any picture above to see larger, higher def images.

For more about this Knotty Pine Offset Barncaster Project, see Part 1, Part 3, and Part 4.

Knotty Pine Offset Barncaster Project, Part 1: A Solid Body Acoustic

It's time for a change - up to now this nicely aged 29 year old 1991 MIM Stratocaster neck has been on the original '91 Strat, and then a 1995 MIJ Fender '57 reissue Stratocaster body. It looks pretty cool in the above photo, attached to a lightweight rustic rough cut reclaimed pine Jazzcaster / Telemaster / Offset Telecaster body from NoMoonLaser in Omaha, Nebraska.

For a while now, there's been a small pile of assorted Tele parts in a bin out in the Alley Gadget Shop garage work area disaster zone, and it seemed like a good time to see what interesting creation we can come up with. In the above photo, besides the neck, there's a Fender Vintage series bridge plate, a Fender '62 model bridge pickup, Wilkinson compensated brass saddles, Fender strap buttons, and an Allparts Electrosocket output jack thingie - all brand spankin' new. Not so visible, on the back are Gotoh string through body ferrules and a Fender "F" neck plate. Also, new Fender Vintage tuning machines just got put on the headstock, using the previously installed Stew-Mac adapter bushings.

After screwing all that stuff down onto the pine body (with appropriately sized pilot holes drilled first), I strung it up with a "set" of new but odd left-over assorted gauge strings, aligned the neck with the bridge, set the action and tweaked the intonation.

Good enough to play, and I have - every day and night for a week now. No need to plug it in, the ultra resonant body on this guitar sounds great acoustically: loud, balanced, bright and snappy, with amazing sustain. After everything else gets installed and hooked up, there's no reason why it shouldn't have really fine electric tone too.

Here's a pile o' parts:

In the pic below are a Warmoth pickguard with a Fender Tex Mex Telecaster neck pickup, and a Fender Tele control plate with a Fender 3-way switch, a pair of CTS 250K potentiometers, and two Gotoh high knurl dome knobs, also all new stuff:

As you can see, the mounting holes haven't been drilled yet for the pickguard and control plate. It was getting late, there was barely enough light coming through the big window for a decent picture before dusk fell. Oh well, there's always tomorrow...

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Click or tap on any picture above to see larger, higher def images.

For more about this Knotty Pine Offset Barncaster Project, see Part 2, Part 3, and Part 4.

McGohan M102 Tube PA Amplifier Schematic

Lately I've been working on an early 1960s McGohan M102 tube type PA / paging amp, and finding a schematic for one of these beasts online is really difficult. Luckily I had a schemo for a McG 102 squirreled away on a backup drive, and here it is, for anyone who might need it.

I don't really know how to embed this GIF file at full size, here in Blogger; the pic above is a somewhat reduced version. However, if you click on the image, it will appear larger; and if you have an iMac, MacBook or similar, you can then "drag and drop" to capture it full size. No doubt Windoze folks and mobile phone users can do something similar, maybe (select, copy, paste?). As an alternative, if anyone would like the full size file, go ahead and get in touch through the "Contact" link over on the right-hand sidebar, and I'll be happy to send it to you via email.

Note also that this schematic is for the McGohan M102-B model, which differs from the earlier M102 (which I have) by having a solid state diode rectifier instead of a 6CA4 (EZ81) vacuum tube rectifier. Besides that one difference, both models appear to be the same - with the exception of the power supply, the circuitry of my M102 is identical. Or at least it was, before I stripped and rebuilt it with a '50s "Tweed"-ish guitar amp circuit.

Cheers, and happy soldering!

Petri 2.8 Color Corrected Super Rangefinder 35mm

The photos in the previous three posts are scans of 35mm Kodacolor prints, taken with a Petri 35mm camera. Made by Kuribayashi Camera Industry Inc, in (where else?) Japan, the Petri 2.8 Color Corrected Super has a style reminiscent of a Leica, the preeminent compact camera of its day, which also had rangefinder assisted focusing.

The Petri 2.8 was my father's first 35mm camera, bought new in Japan when he was stationed with the US army in South Korea during the mid 1950s. It was also my first 35mm camera; after his untimely death, I found the Petri among my dad's effects and sort of "self inherited" it, the only memento of his that I kept.

By the early 1970s, the Petri was already obsolete; in the 15 years since its manufacture, the state of the art for semi-pro and professional level cameras had become the single lens reflex interchangeable lens 35mm, popularized by the Asahi Pentax and Nikon F. The now out of date Petri had only a fixed-mount 45mm f2.8 lens, but as many photo enthusiasts have discovered, it was in a way liberating to be restricted to the use of only one, normal field of view, prime lens. That limitation meant no telephoto shots of wildlife or wide angle panoramic views, but whatever one's own eyes saw, the Petri recorded that very well.

Compact enough to fit easily in the outside pocket of a sport coat or field jacket, the Petri was always readily at hand to grab a quick shot, and its whisper quiet leaf shutter was a lot less likely than a loud clanking SLR to suddenly freeze a rocking party cold dead. This camera didn't have a built in light meter, and I eventually bought a small Sekonic handheld, but I'd already gotten good at guesstimating exposure with the Sunny 16 Rule, and the meter was rarely used.

As you can see, even though it's ancient, this camera is still in very good condition. There used to be a beautiful two-piece brown leather form fit case, which did its job well - in fact that case died in the line of duty, literally falling apart while protecting its precious cargo. I gave the case, along with the original strap, a proper burial with full honors, at dawn in Monument Valley. Coincidentally, after returning from that trip, I bought my first single lens reflex 35mm camera, a Honeywell (Asahi) Pentax, followed soon thereafter by a new Canon AE-1 with multiple lenses, and my photos were never the same again. More precise and accurate, certainly, but most if not all of the indefinable magic and mystery of the Petri's photographs had gone.

I ran a lot of rolls through it back in the film days, and what's interesting is- the Petri took very sharp and clear black and white photos (usually Kodak Plus X or Tri X, and sometimes Agfa), but with Kodacolor the prints were not quite exactly focused looking. Rather than being perfectly detailed, the Petri's color images were pleasing in a diffused, dream-like kind of way. Sort of how memories seem to be.

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To see images taken with the Petri 2.8 rangefinder camera, go to:

Un jour à La Pointe de Fermin, 1972

One Evening At The East Rim Of Lake Abert, August 1973

Petri Kodacolor Portraits

Petri Kodacolor Portraits

The C&W Express: Harry, Harley, and Paul. Kearny, Nebraska

Here are a few more Kodacolor photographs taken with the Petri 2.8 Color Corrected Super rangefinder camera. Each photo has a story behind it, some of which are a short paragraph long, others somewhat longer, and a couple are 200+ page novel length. Maybe someday they'll be retold, but for now we'll just let the images stand alone, and be as expressive as a Kodacolor print from the last century can be.

Dave. Bishop, California

Martha. St Paul, Minnesota

Larry. Minneapolis, Minnesota

Jacqui. Glendive, Montana

Zoe. Fort Collins, Colorado

Dick. Minneapolis, Minnesota

Chester. Loveland, Colorado

Cathy and Serge. Bishop, California

Michael. Loveland, Colorado

Chester, Judy and Rita. Yellowstone, Montana

Harry. Glendive, Montana

Karen. Fort Collins, Colorado

Little Baby Jesus. Wheatland, Wyoming

Wayne and Friend. Loveland, Colorado

The Author as a Young Man. Orofino, Idaho

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The last photo above wasn't taken with the Petri 2.8, although it is a Kodacolor print. It was snapped by Billy with his brand new Kodak Instamatic 110, which at the time was state of the art for affordable pocket cameras, and actually took quite decent images, considering its smaller size film format and low price.